Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be accessed by various types of access terminals adapted to facilitate wireless communications, where multiple access terminals share the available system resources (e.g., time, frequency, and power). Examples of such wireless communications systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems and orthogonal frequency-division multiple access (OFDMA) systems.
As access terminals and network devices communicate over an air interface in a wireless communications system, data is typically divided into smaller packets (or data blocks). Data may also be encoded for transmission with an error detection code so that the receiver can detect erroneous or lost packets and thereby request retransmission. In various wireless communications systems, ACK/NACK messages are sent by the receiving device to the transmitting device to indicate whether there was an error in the transmission detected by the receiver. An acknowledgment (ACK) can indicate that the identified packet has been successfully received. A negative acknowledgment (NACK) can indicate an error in the transmission detected by the receiver. In response to a NACK message, the transmitter may retransmit the relevant packet(s).